The usual etiquette is if the occupants of the car want you to approach they will flash their lights, not that I'm an expert!
It's far too dangerous to go dogging these days unfortunately, and I'm sure you don't have to think too hard to know why.
I would say it's just as dangerous for men today...
I seem to remember there was a website with dogging locations, I used to do it a number of years ago and it was a lot of fun, but sadly in this day and age you just don't know who is sleeping in the woods,
I find the whole site a bit "sticky". My posts tend to be posted twice as I'm not sure I sent it on the first click.
My laptop is old and sluggish anyway so it could be me, but other websites I visit work just fine.